The present invention relates to an integrated system that produces an indirect measurement of the sign of the current that flows into/out-of an inverter driving a motor and is able to sense the counter Electromotive Force (EMF) voltage induced in a coil of the motor by measuring a phase voltage.
Motor drive applications make wide use of inverter bridges for providing voltage to the motor. Inductive characteristics of the motors of these motor drive applications are such that coil currents keep flowing into the inverter stage for a while, before decaying to zero. In particular, this is true for both AC induction and brushless motors. Moreover, for brushless motors under particular conditions, the counter or back EMF induces a voltage on the phase nodes which is proportional to a mechanical speed of the motor.